High-speed varifocal objective



35o-427 5R SEARCH ROOM Oct. 10, 1967 K. H. MACHER 3,346,320

HIGH-SPEED VARIFOCAL OBJECTIVE Filed July 17, 1963 KARL H. MACHERJnvenor:

AGENT.

United States Patent O 3,346,320 HIGH-SPEED VARIFOCAL OBJECTIVE Karl H.Macher, Bad Kreuznach, Rhineland, Germany,

assignor to Jos. Schneider & Co., Bad Kreuznach, Germany, a corporationof Germany Filed July 17, 1963, Ser. No. 295,851 2 Claims. (CI. 350-184)My present invention relates to a varifocal optical objective system forphotographic or cinematographic cameras, the system including a fixedrear lens group and an adjustable front lens group of the general typedisclosed in commonly assigned copending application Ser. No. 126,306led July 24, 1961, by Gnter Klemt and me, since abandoned and replacedby application Ser. No. 420,727 filed Dec. 23, 1964, now Patent No.3,272,073.

One of the systems disclosed in the prior application above referred tohas a varifocal ratio of 6:1 and a relative aperture of 1:l.4,corresponding to a focal length ranging between about 40 and 240 mm. inan object of this type.

The general objective of my present invention is to provide `a system ofthis type which, with like frame sizes, operates on shorter overallfocal lengths while still maintaining substantially the same largevarifocal ratio. An advantage of this shift of the focal range is theincreased field angle thereby obtainable.

A more particular object of the invention is to bring about the desiredreduction in overall focal length without materially reducing the focallength of the fixed rear lens group constituting, as it were, a basic orprincipal objective for which the adjustable front lens group acts as avarifocal attachment; a major decrease in the focal length of this rearlens group is often objectionable in that it increases the angle ofincidence of slanting rays, thereby necessitating larger lens diametersin the front component of the system, hence the invention aims atobviating this drawback.

Another object of this invention is to provide an objective system ofthis character which is focusable, without the need for a separateattachment, onto nearby objects (eg. as close as l m. or less) withoutchanges in the backfocal length of the objective, with illumination ofthe entire field of projection and with only a small adjustment strokeof a limitedly displaceable focusing lens.

An objective system according to the present invention consists of afour-component forward lens group and a four-member rear lens group, themembers of the forward lens group including two stationary positivelyrefracting components bracketing two axially movable negativelyrefracting components as is well known per se; the positive firstcomponent of the forward lens group includes a dispersive front lens,which is preferably adjustable, and one or more collective lensesseparated from this front lens by an air space whose axial extent isless than one-fourth of the focal length of said first component, thisfocal length in turn being greater than the individual focal length ofthe negative front lens.

The collective portion of the first component preferably consists ofthree air-spaced positive singlets whose confronting surfaces are sodimensioned that the sum of the reciprocal values of the radii ofcurvature of the surfaces 3,346,320 Patented Oct. 10, 1967 ICC theadjustment stroke of that front lens is very short even for focusing atclose range (e.g. less than 1 m.); at the same time the diameter of thisfront lens, as also those of the three positive lenses following it, isof only moderate size compared with the total axial length of thesystem.

The sole figure of the accompanying ydrawing illustrates an embodimentof my invention.

The system shown in the drawing comprises a fourcomponent varifocalforward lens group I-IV and a fixedfocus four-component rear lens groupV. The first component I of the varifocal group comprises a dispersivelens L1 with radii r1, r2 and thickness d1, separated by an air space d2from an assembly of three closely juxtaposed collective singlets, i.e. afirst biconvex lens LZ with radii r3, r4 and thickness d3, a secondbiconvex lens L3 with radii r5, r6 and thickness d5, and a positivemeniscus L4 with radii r7, r8 and thickness d7; the intervening airspaces have been designated d4 and d6. A variable air space d8 separatesthe positively refracting first component I from the axially shiftable,negatively refracting second component II which consists of a nearlyplanoconcave lens L5 (radii r9, r10, thickness d9) and a doublet airspaced from lens L5 by a distance d10, this doublet being constituted bya substantially plano-convex lens L6 (radii r11, r12, thickness dll)cemented onto a biconvex lens L7 (radii r12, r13, thickness d12).Another variable air space d13 intervenes between components II and III,the latter being an axially shiftable doublet consisting of asubstantially plano-concave lens L8 (radii r14, r15, thickness d14) anda substantially plano-convex lens L9 (radii r15, r16, thickness d15)cemented thereto. The fourth component IV, following component III witha variable spacing d16, is a fixed positive lens L10 of nearlyplano-convex configuration having radii r17, r18 and thickness d17.

Component V follows the group I-IV with a spacing d18, the four membersof .this component being a substantially biconvex lens L11 (radii r19,r20, thickness d19), another positive lens L12 of similar configuration(radii r21, r22, thickness d21) spaced from lens L11 by an air gap d20,a negative doublet composed of a biconcave lens L13 (radii r23, r24,thickness :123) and a concavo-convex lens L14 (radii r24, r25, thickness124) cemented to it, this doublet being separated from lens L12 by anair space d22, and a biconvex singlet L15 (radii r26, r27, thicknessd26) following the doublet L13, L14 with a spacing d25.

Representative numerical values for the radii r1-r27, the thicknessesand air spaces d1-d26, the refractive indices nd and the Abb numbers vof a system as shown in the drawing, constituting an objective withrelative,

aperture of 1:1.4 and varifocal range of 30 to 180 linear o units (eg.millimeters), are given in the following table:

TABLE-Continued Thicknesses Lens Radii and nd y separations d8 =155.70Variable air space r9 =+l0,000.00 L d0 =7.50 1. 62041 00. 29

d10=15.50 Airspace 11-.--. r11=1,502.00 1

L6. d1l=l7.00 1. 80518 25. 46

d13=34.80 Variable air space r14=66.00 L8.. d14=4.00 1.62041 60. 29 IIIr15=+872.75

dl6=30.00 Variable air space r17=+l,002.00 IV L10.-. d17=11.00 1. 6584450. 84

rl8=l26.25

dl8=38.00 Air space r19=+102.80 L11 d19=10.75 1. 71300 53.89

d20=0l50 Air space r21=+62.95 L12.-- d2l=17.00 1. 71300 53. 89

d22=1.50 Air space V r23=-475.00

r24=+38.93 L14. d24=15.00 l. 71300 53. 89

12S-:16.25 Air space 126=+100-50 'L15 d26=10.75 1. 71300 53. 89 ir27=-124.65

The front lens L1 has an individual focal length fL1=265 whose absolutevalue is less than that of the focal length f1=l295 of the frontcomponent I. It will be noted that the latter focal length f1 is morethan four times as large as the air space d2 separating lens L1 from thenext lens L2, the extentl of this space in the normal position ofadjustment of lens L1 (i.e. with focus at infinity) being 56.5 linearunits.

The values given in the foregoing table also satisfy the relationship 12 l l 2 n a f6 fr) which is to be observed for the suppression ofresidual aberrations, r4 and rS being the radii of curvature of lensfaces bounding the air space d4 whereas r6 and r7 are the radii of thecorrespondent lens faces adjoining the air space d6. The magnitudes ofthe variable air spaces d8, d13 and d16 given in the table,corresponding to the lens positions shown in the drawing, represent anadjustment to an intermediate overall focal length f=100. For theminimum focal length f=30, the numerical values of these air spaces willbe d8 9.25 dl3=187.40 d16= 23.85

for the maximum focal length f=180, thesevalues will be d8 :200.60 d13=14.70 d16= 5.20

I claim:

1. In an optical objective system including a fixedfocus rear lensgroup, the combination therewith of a forward lens group consisting of asubstantially fixed positive first component, a negative secondcomponent, a negative third component and a fixed positive fourthcomponent; said first component including three air-spaced positivesinglets and a dispersive front lens preceding said singlets, said frontlens being air-spaced from the next one of said singlets by a distanceless than substantially one-fourth of the focal length of said firstcomponent,

said front lens having an individual focal length whose absolute valueis less than that of the focal length of said firstcomponent; saidsecond and third components being movable, relatively to each other andto said first and fourth components, into a first position in which thesystem has a relatively small focal length, an intermediate secondposition, and a third position in which said system has a relativelylarge focal length, said second component consisting of a negativesinglet followed by a negative doublet, said third component being anegative doublet; the numerical values of the radii of curvature r1 tor18 of said dispersive front lens L1, said collective singlets L2, L3,L4, said negative singlet L5 of said second component, said doublet L6,L7 of said negative second cornponent, said doublet L8, L9 of said thirdcomponent and Aa positive singlet L10 constituting said fourthcomponent, and of the axial thicknesses and separations d1 to d17thereof, based upon a numerical value of for an intermediate overallfocal length of the system, the refractive indices nd of said lenses andtheir Abb numbers v being substantially as given in the following table,the spaces d8, 113 and d16 being given for that second position:

TABLE Thiclrnesses Lens Radu and nd separations r1 =-1,339.00 LIU.. ril=15.00 1.78470 26.10

d2 =56.50 Airspace r3 =+3S5.40 L2 d3 =30.00 1. 69033 49.57

r4 =1,434.00 I d4 =0.90 Air space f5 =-|-1,025 00 L3 d5 =25.75 1.6779055.52

d6 :1.35 Air space f7 =+3os.so L4 (17 =22.50 1.67790 55.52

d8 =155.70 Alr space r9 =|l0,000.00 L5 (19 =7.50 1.02041 00.29

dl0=15.50 Air space II rl1=-1,502.00

L6. 4- dll =l7.00 1. 80518 25. 46

rl2=-160.70 L7. dl2=5.00 1. 52542 64. 55

d13=34.80 Air space r14=66.00 L8 dl4=4.00 1. 62041 (i0` 20 IIL-..rl5=+872.75

d16=30.00 Air space rl7=+1,002.00 IV L10..- dl7=11.00 1.65844 50.84

2. An optical objective system comprising a rear lens group consistingof four fixed air-spaced lens members and a forward lens groupconsisting of a substantially fixed positive first component, a negativesecond component, a negative third component and a fixed positive fourthcomponent; said first component including three air-spaced positivesinglets and a dispersive front lens preceding said singlets, said frontlens being air-spaced from the next one of said singlets -by a distanceless than substantially one-fourth of the focal length ofV said firstcomponent, said front lens having an individual focal length whoseabsolute value is less than that of the focal length of said firstcomponent; said second and third components being movable, relatively toeach other and to said first and fourth components, into a firstposition in which the system has a relatively small focal length, anintermediate second position, and a third position in which said systemhas a relatively large focal length, said second component consisting ofa negative singlet followed by a negative doublet, said third componentbeing a negative doublet, said rear lens group consisting of a firstpositive lens member, a second positive lens member, a cemented negativelens member and a third positive lens member all air-spaced from oneanother; the numerical values of the radii of curvature r1 to r27 ofsaid dispersive front lens L1, said collective singlets L2, L3, L4, saidnegative singlet L5 of said second component, said doublet L6, L7 ofsaid negative second component, said doublet L8, L9 of said thirdcomponent, a positive singlet L constituting said fourth component,the'rst positive lens member L11 of said rear group, the second positivelens member L12 of said rear group, the cemented lens member L13, L14 ofsaid rear group and the third positive lens member L of said rear group,and of the axial thicknesses and separations d1 to d26 thereof, basedupon a numerical value of 100 for an intermediate overall focal lengthof the system, the refractive indices nd of said lenses and their Abbnumbers v being substantially as given in the following table, thespaces d8, d13 and d16 being given for said second position:

TAB LE Thicknesses Lens Radii and nd v separations r1 =-1,339.00 L1...-d1 =15.00 1. 78470 26.10

d2 =56.50 Air space r3 =+385A0 L2. d3 =30.00 1. 69938 49. 57

r4 =1,434.00 I d4 :0.90 Air space f5 =+1,02b.00 L3 d5 =25.75 1. 6779055. 52

d6 =1.35 Air space T7 =+308.80 L4..-. |17 =22.50 1.67790 55. 52

d8 =155.70 Air space r9 =+10,000.00 L5- d9 =7.50 1. 62041 60.29

d10= 15.50 Air space II...-. rl1=1,502.00

L6 dll 17.00 1. 80518 25. 46

r12= -160.70 L7 d12=5.00 1. 52542 64. 55

TABLE-Continued Thicknesses Lens Radii nd 5 Separatlons l d13=34.80 Airspace r14= 66.00 L8 d14=4.00 1. 62041 60. 29 111-... r15=+872.75

L9.. d15=10.50 1. 64831 33. 77 10 r16= -16825 d16=30.00 Air spacer17=+1,oo2.0o IV-. L10- d17=11.00 1.65844 50.84

1118 =38.00 Air space r19=+102.80 15 L11 d19=10.75 1. 71300 53.89

d20=0.50 Air space T21 =+62.95 L12` d21 =17.00 1. 71300 53. 89

d22=1.50 Air space V. r23=475.00 20 L13 d23=7.75 1. 8051s 25. 46

r24=+38.93 L14.-- d24=15.00 1.71300 53.89

d25=16.25 Air space r26=+100-50 L15 d26=10.75 1. 71300 53. 89 25r27=124.65

References Cited 30 UNITED STATES PATENTS 3,272,073 9/1966 Klernt et al.88-57 FOREIGN PATENTS 1,247,678 10/ 1960 France. 1,309,648 10/1962France. 1,311,131 10/1962 France.

JEWELL H. PEDERSEN, Primary Examiner.

R. I. STERN, Assistant Examiner.

1. IN AN OPTICAL OBJECTIVE SYSTEM INCLUDING A FIXEDFOCUS REAR LENSGROUP, THE COMBINATION THEREWITH OF A FORWARD LENS GROUP CONSISTING OF ASUBSTANTIALLY FIXED POSITIVE FIRST COMPONENT, A NEGATIVE SECONDCOMPONENT, A NEGATIVE THIRD COMPONENT AND A FIXED POSITIVE FOURTHCOMPONENT; SAID FIRST COMPONENT INCLUDING THREE AIR-SPACED POSITIVESINGLETS AND A DISPERSIVE FRONT LENS PRECEDING SAID SINGLETS, SAID FRONTLENS BEING AIR-SPACED FROM THE NEXT ONE OF SAID SINGLETS BY A DISTANCELESS THAN SUBSTANTIALLY ONE-FOURTH OF THE FOCAL LENGTH OF SAID FIRSTCOMPONENT, SAID FRONT LENS HAVING AN INDIVIDUAL FOCAL LENGTH WHOSEABSOLUTE VALUE IS LESS THAN THAT OF THE FOCAL LENGTH OF SAID FIRSTCOMPONENT; SAID SECOND AND THIRD COMPONENT BEING MOVABLE, RELATIVELY TOEACH OTHER AND TO SAID FIRST AND FOURTH COMPONENTS, INTO A FIRSTPOSITION IN WHICH THE SYSTEM HAS A RELATIVELY SMALL FOCAL LENGTH, ANINTERMEDIATE SECOND POSITION, AND A THIRD POSITION IN WHICH SAID SYSTEMHAS A RELATIVELY LARGE FOCAL LENGTH, SAID SECOND COMPONENT CONSISTING OFA NEGATIVE SINGLET FOLLOWED BY A NEGATIVE